Labor leader and soon-to-be opposition leader Shelly Yacimovich declared Monday night that her party would lead the opposition with "energy and with faith," after Prime Minister Binyamin Netanyahu struck a deal with opposition leader Shaul Mofaz that will draw Kadima into the coalition.

"We have been given a rare and important opportunity to head the opposition, and we will do so with energy and with faith," she said.

"It is a covenant of cowards between Netanyahu and Mofaz," Yacimovich said of the agreement, which was announced late Monday night just as a bill to dissolve the Knesset was headed to the plenum for its final reading.

"This is the most ridiculous, disgusting zigzag in Israeli political history," she charged.

Labor MK Isaac Herzog said the unity government gave Labor a prime opportunity to lead the nation as the main opposition party. Speaking with Israel Radio, Herzog said he was confident the Labor could now win in elections in 2013.

Yair Lapid - whose just-founded Yesh Atid Party was seen as a chief rival against the centrist Kadima - also slammed the unity government proposal, calling the new coalition a "disgusting political alliance."

"What you saw today are the old politics, dim and ugly, of which we should rid ourselves," Lapid wrote on his Facebook page Tuesday morning. "It is a politics of chairs instead of principles, of jobs instead of the public's welfare, of one group's interests instead of those of the entire country."

"They think we will forget but they are wrong," he continued. "This disgusting political alliance will bury beneath it all its members." The deal will keep Lapid's party out of the Knesset until the next round of elections.

Some in Likud also opposed the deal, which will see the Kadima party gain ministerial positions in the government and head a committee tasked with approving an alternative for the contentious Tal Law.

Likud MK Danny Danon said the deal betrays his party's voters.

"Likud's values have been violated," he charged. "And so has the public that voted for Likud and got Kadima and [Defense Minister Ehud] Barak."

Danon complained that the move will embolden the defense minister "for the next year and a half."

"[The agreement] will damage the settlement movement, cause injury to Likud's values and to the Israeli public that elected Likud to lead Israel," he said.

Coalition head Ze'ev Elkin countered Danon, however, saying "no Likud values have been sacrificed. The deal on the Tal Law can be reached with haredim. Only a unity government can bring a solution on the Tal Law, and the government system," two items Kadima has been tasked with tackling as part of the coalition.

Education Minister Gideon Sa'ar told reporters after the announcement that there was no need for early elections anymore.

"The deal will bring political stability and help Israel deal with the coming security and economic challenges," he said.

"I don't care that we're saving Kadima. We are killing Lapid and Livni," Environmental Protection Minister Gilad Erdan said, referring to the Yesh Atid leader and Tzipi Livni, who lost the Kadima party chair to Mofaz in primary elections last month.

Shas leader Eli Yishai, meanwhile, said he was aware of the deal - which was announced suddenly just as the Knesset was set to vote to dissolve the government - all along.